1. Field of the Invention
This invention relates generally to integrated circuits, and more particularly to integrated circuit thermal management systems.
2. Description of the Related Art
Many types of currently-available integrated circuits are mounted on a substrate, which is in turn affixed to a printed circuit board or other type of mounting structure. Following attachment to the printed circuit board, the integrated circuit is covered by a lid, which provides not only a protective covering for the integrated circuit but may also facilitate the transfer of heat from the integrated circuit to one sort of cooling structure or another. In the testing context, a thermal control system or “heater” is usually positioned on the lid. The heater is operable to maintain the temperature of the integrated circuit within some selected range while the integrated circuit is subjected to electrical and other types of performance testing. Such testing frequently subjects the integrated circuit to more rigorous conditions than would be encountered in actual circuit operation. Accordingly, the thermal control system is used to prevent the temperature of the integrated circuit from spiraling upward and causing chip failure.
Accurate knowledge of the thermal environment of an integrated circuit and its corresponding lid is important from both a testing and manufacturing standpoint. In this regard most present day integrated circuits include an onboard diode that serves as a temperature measuring device. Many conventional heaters also include an onboard thermal diode that is positioned on the upper surface of the heater. Of course, the difficulty with the conventional set up is that while the onboard diode on the integrated circuit provides a relatively good measure of the temperature of the integrated circuit and while the onboard thermal diode on the thermal control system provides a similarly acceptable measurement of the temperature of the thermal control system, neither provides an acceptably accurate measure of the temperature of the lid. Interestingly though, the temperature of the lid is often used by electronics manufacturers as a specification for the desired thermal performance of the electronic system in question.
One conventional technique for measuring lid temperature involves using a sensing probe, such as a Type-T thermocouple, in conjunction with a Kryotech-brand heater. The thermocouple is brought into contact with the lid. This technique has the drawback of requiring clear access to the lid, which is usually not feasible if a heater with a complete surface contact is present. Attempts to provide better access for the probe may actually increase the thermal resistance of the heat transfer pathway between the integrated circuit and the heater.
More remote sensing techniques, such as infrared sensing, again rely on a clear pathway between the lid and the remote sensor. Attempts to provide access to the lid for either a contact probe or a remote temperature sensor run the risk of increasing thermal resistance and thus significantly decreasing the ability to control the heating levels of the integrated circuit.
The present invention is directed to overcoming or reducing the effects of one or more of the foregoing disadvantages.